(1) Field of the Invention
The present invention relates to a method for forging articles requiring a single forging such as hollow fan blades for gas turbine engines.
(2) Description of the Related Art
It is current practice to fabricate hollow fan blades, typically fabricated from titanium, for use in gas turbine engines. It is preferable that such fan blades be hollow. By fabricating hollow fan blades, the mass of the fan blades may be substantially reduced resulting in notable efficiencies. Typically the hollow fan blade halves are forged separately, one half corresponding to the pressure side with the other corresponding to the suction side. Once forged, each half is substantially machined to create the airfoil contour, the airfoil root block, datum features such as holes, hollow cavities, and diffusion bond surfaces. As noted this is done for both the pressure side and the suction side from each oversize “pancake” forging. The suction side and the pressure side are then subsequently diffusion bonded together to make a single hollow fan blade.
The use of diffusion bonding in turbine blade formation is well known. An example may be found in U.S. Pat. No. 5,711,068, the disclosures of which is incorporated by reference herein as if set forth at length. The '068 patent discloses a specific situation in which two blade halves are cut from a single piece and are diffusion bonded with uncut surfaces facing each other.
Such a process requires extensive machining time to achieve both the airfoil contour and the root block. In addition, a significant amount of scrap titanium is generated. What is therefore needed is a method for forging hollow fan blades, particularly titanium fan blades, which requires less machining and results in a reduction in the amount of scrap titanium generated.